This invention relates to exercise machines that simulate weight lifting wherein resistance is provided by spring action and more particularly it relates to controlling the resistance.
Exercising one""s muscles has progressed from free weights to machines where creative assembly of weights and cables enables a person to exercise most if not all of the muscles of his/her body. Athletic clubs offer as many as 20 or more different types of machines whereby a person can progress from machine to machine and direct the exercise to different muscles of different body parts. A person can readily vary the effected weight resistance by moving a pin that adds or subtracts the number of weights that produce the resistance.
Whereas athletic clubs are desirable for a substantial segment of the population, there is a demand for home exercising machines as well. It is not generally feasible for individuals to equip their home with these same machines. Such are expensive to purchase, expensive to ship due to the bulk and weight, and substantial home space has to be dedicated to machine use only.
A large dedicated space and numerous machines are quite acceptable for an athletic club as such accommodate numerous users of the machines, the users simply staggering their time of use and sequentially cycling through the different machines. Home use on the other hand is typically a single user and space and cost are important considerations. Accordingly, home use exercising machines have been developed whereby a single machine having a creative arrangement of cables and pulleys with relatively simple adjustments thereof can provide variable resistance applicable to a wide range of user muscles. The weights of the athletic club exercising machines are replaced, e.g., with spring members that provide the desired resistance for exercise but which have only a fraction of the true weight of xe2x80x9cweightsxe2x80x9d used for the athletic club machines. Shipping costs are dramatically reduced and the machines can be more readily moved by the home owner/user, e.g., to storage or from room to room. A guest room may be convertible as desired for guest use or for exercise use as but one example. Such a machine is hereafter sometimes referred to as a universal machine.
One problem with the use of spring members to replace the xe2x80x9cweightsxe2x80x9d is that a spring member varies in its resistance as the spring member is deflected. A pull cable acting to deflect the spring (deflect here encompassing compression, tension, bending, etc.) may require an increasing force, e.g., a force of 5-10 pounds over the first several inches of deflection, 10-15 pounds of force over the next several inches of deflection, etc. To this extent, the spring members do not equate to a free weight which requires a constant pull force over whatever length of pull is required for the particular exercise. It is accordingly an objective of the present invention to provide a universal exercise machine that utilizes a spring force versus xe2x80x9cweightsxe2x80x9d while providing a steady resistance to a cable pull against the spring action to simulate a true xe2x80x9cweight.xe2x80x9d Thus, the resistance that the user experiences remains constant throughout the entire range of deflection, even though the actual resistance provided by the spring member increases as greater deflection occurs. Alternatively the resistance may be xe2x80x9cshaped,xe2x80x9d i.e., to generate an increasing resistance or decreasing resistance or combination of increasing and decreasing resistance as may be desired for a particular exercise. xe2x80x9cShapedxe2x80x9d resistances refer to dynamically changing resistances that are xe2x80x9cfeltxe2x80x9d by the user during an exercise. Each xe2x80x9cshapedxe2x80x9d resistance can be thought of as a resistance curve that shows the range of movement caused by the user and the corresponding xe2x80x9cfeltxe2x80x9d amount of resistance.
In the preferred embodiment, the spring action is provided by an elongate spring member. The spring member is preferably a cylinder of elastomer having the property of being resistively and resiliently compressible. The spring member is not limited to a cylinder of elastomer, and it will be understood by those skilled in the art that other types of compressible cylinders may be used, such as a conventional spring, gas spring, etc. It may be confined in a tube that permits collapse/compression and prevents bending to thereby permit axial compression only of the elastomer cylinder. It is desirable that the range of forced differential, i.e., the force required to deflect the cylinder at the start of the cable pull versus the force of cable pull at the end of the cable pull be minimized and this is accomplished by precompressing the cylinder. Thus, with the tube at full extension, the cylinder in the tube is held to the precompression load. Alternatively, the cylinder may be skewered on a rod and sandwiched between washers. Precompression can be accomplished by providing a stop at one end and a nut threaded on the other end, the nut turned to shorten the distance between the washers to thereby compress the cylinder.
The resistance of the cylinder to further compression nevertheless still varies (gets stronger) and an arrangement is provided to counter this variation. A cable extends from the user""s lifting bar or rings or foot pedal or whatever that is to be moved by the user to exercise a particular set of muscles. The cable is directed through pulleys as necessary to direct the cable from an overhead position to a lift arm. The lift arm is secured at one end to a rotatable pin or axle and the other end is connected to the cable. Pulling of the cable upwardly achieves pivoting of the lift arm about the axle axis as well as rotation of the axle. Also affixed to the axle is one end of an abbreviated (relatively shorter) pivot arm having a lift roller at its distal end. The lift roller engages the under side of a formed pivotal bar spaced from the point of pivoting. The elongate collapsible tube containing the elastomer cylinder is pivotally attached at one end at a position above the pivotal bar with the opposite end extending down to and engaging the pivotal bar also spaced from the point of pivoting.
In order to pull the cable, the lift arm has to be raised producing pivoting of the axle. This produces raising of the lift roller which acts against the formed pivotal bar to pivot the formed bar about its axis which is only accomplished by compressing the tube and cylinder.
The arrangement described provides a number of variables, the most important perhaps being the arc of movement by the abbreviated pivot arm. For a given distance of cable pull, the abbreviated pivot arm is pivoted through an angular arc. For explanation purposes, assume that the lift roller and pivot arm at the start of the pull extend to a 9 o""clock position and is pivoted to a 12 o""clock position. The resistive force of the formed bar is assumed (for explanation purposes) to produce an effective force directed vertically downward. The total vertical distance that the lift roller is assumed to travel is three inches (which is also the distance the roller moves horizontally).
It will be further assumed that the total distance of cable pull to affect the 90 degree pivotal movement of the pivot arm is 42 inches, i.e., the cable pull is 14 inches for each 30 degrees of rotation of the pivot arm. During the first 14 inches of cable pull, the pivot arm is rotated 30 degrees, i.e., from the 9 o""clock position to the 10 o""clock position. Whereas only one-third of the rotation has been completed, essentially half of the vertical distance has been completed, i.e., the formed bar has been raised about one and one-half inches with one-third the pull of the cable. The remaining one and one-half inches of vertical lift is accomplished through 60 degrees rotation of the pivot arm and 28 inches of pull of the cable. Thus, the load experienced by the user tends to get smaller (due to the changing angular direction of movement of the lift roller relative to the formed bar). As previously explained, the necessary force to compress the elastomer cylinder increases throughout compression and these variables offset one another.
The above is a somewhat simplified explanation but once the concept is appreciated, it will be understood that manipulation of such factors as lever length and point of engagement of the lift roller with the formed bar and the shape of the bar itself provides the opportunity to control the variables and xe2x80x9cshapexe2x80x9d the applied resistance to a particular exercise selected by the user. The invention will be more fully understood and appreciated upon reference to the following detailed description of the preferred embodiment and the accompanying drawings.